Transmission power control during simultaneous communications

ABSTRACT

In a method for communication between a first station (BS 1 ) and a second station (MS 1 ) the first station may provide the second station with information associated with the manner how the second station should transmit towards the first station. The second station (MS 1 ) may then transmit e.g. a response to a message from the first station (BS 1 ) based on said information. That is, the second station (MS 1 ) may e.g. use a specific transmission parameter for the transmission instead of transmitting in a manner the second station would have transmitted had it not been provided with said information. A communication system and stations for the communication system embodying the method are also disclosed.

FIELD OF THE INVENTION

The present invention relates to a communication system, and inparticular, but not exclusively, to transmissions between stations of acommunication system.

BACKGROUND OF THE INVENTION

Various different communication systems adapted to provide wirelesscommunication between two or more stations are known. Wirelesscommunication media may be provided between a station of a communicationnetwork and a user equipment. Wireless communication media may also beprovided between two user equipment or between two stations of acommunication network.

A wireless communication system may be used for various types ofcommunication, such as for voice communication or data communication. Awireless system may provide circuit switched or packet switched servicesor both. In packet switched services data (e.g. speech data, user data,video data or other data) is communicated in data packets. Thedevelopment in the wireless communication has lead to systems that arecapable of transporting data in substantially high data rates i.e. theso called high speed data (HSD).

An example of wireless communication systems is a cellular communicationsystem. In a cellular system the user equipment may access thecommunication network via access the communication network via accessentities referred to as cells, hence the name cellular system. Theskilled person knows the basic operational principles and elements of acellular network and these are therefore not explained herein in anygreater detail. It is sufficient to note that a cell can be defined as aradio access entity that is served by one or several base stations (BS)serving user equipment (UE) via a wireless interface therebetween.Examples of the cellular networks include networks that are based onaccess systems such as the CDMA (Code Division Multiple Access), WCDMA(Wide-band CDMA), TDMA (time Division Multiple Access), FDMA (FrequencyDivision Multiple Access), or SDMA (Space Division Multiple Access) andhybrids thereof.

A wireless communication system is typically provided with a radioresource management function. A feature of the radio resource managementis that it may continuously adjust the use of resources such as thepower levels between a base (transceiver) station and user equipmentassociated with said base station during communication between the basestation and the user equipment. Use of radio resources may be controlledfor transmissions that occur from the base station towards the userequipment (downlink) and from the user equipment towards the basestation (uplink). The adjustment is done in order to provide asufficient quality and reliability for the transmission between the basestation and the user equipment in various conditions and, on the otherhand, to reduce power consumption and interference caused by thecommunication to other devices.

A user equipment may communicate simultaneously with a number of basestations. FIG. 1 shows an example where a user equipment MS1 is incommunication with two base stations BS1, BS2. The simultaneouscommunication with a plurality of base stations may occur, for example,when a user equipment is to be handed over form a base3 station toanother base station.

The handover may be performed by means of the so called soft handoverprocedure. For example, in the CDMA soft handover may be used to reducethe Interference caused by the user equipment. During a soft handoverthe transmission power of a user equipment is typically adjusted basedon power control commands from a base station that request for thelowest transmission power. Each base station involved in the softhandover measures the quality of the signal from a given user equipmentand sends its power control commands to the user equipment asking thepower up or down. The user equipment increases its transmission poweronly if all base stations involved in the soft handover request for morepower.

The user equipment may receive data such as control messages, user dataand so on from a base station. The user equipment may receive data frommore than one base station. Some of these data transmissions may need tobe responded by the user equipment. The response may, for example, be anacknowledgement that the user equipment did receive the message and/orthat the user equipment did accomplish a task in response to the messageand/or a response to an inquiry and/or any other feedback that may berequired by the base station. The following will discuss a more detailedexample that relates to acknowledgements in a third generation widebandcode division multiple access (3G WCDMA) system.

In WCDMA based systems the above referred high speed data may be enablede.g. by means of the so called high speed downlink packet access (HSDPA)technology. The high speed downlink packet access (HSDPA) may includefunctions such as fast hybrid automatic repeat request (HARQ), adaptivecoding and modulation (AMC) and/or fast cell selection (FCS). Thesefunctions are known by the skilled person and will thus not be explainedin more detail. A more detailed description of these and other functionof the HSPDA can be found e.g. from a third genera-ion partnershipproject technical report No. 3G TR25.848 release 2000 titled ‘PhysicalLayer Aspects of UTRA High Speed Downlink Packet Access’. It shall beappreciated that although the HSDPA has been specified for use in theWCDMA, similar basic principles may be applied to other accesstechniques.

At the present it is assumed that in the high speed downlink packetaccess (HSDPA) each user equipment receiving data on a high speeddownlink shared channel (HS-DSCH) also has an associated dedicatedchannel (DCH) allocated. The dedicated channel may be mapped to adedicated physical channel (DPCH) in the physical layer. The DPCH istypically divided into dedicated physical data channel (DPDCH) anddedicated physical control channel (DPCCH) both in the uplink and thedownlink. Data such as the power control commands, transport formatinformation, and dedicated pilot symbols are transmitted on the DPCCH.Information such as diversity feedback information may also betransmitted on DPCCH in the uplink. The HS-DSCH may be mapped to one orseveral high speed physical downlink shared channels (HS-PDSCH) in thephysical layer.

The associated dedicated channel is typically provided both in thedownlink and the uplink. The dedicated channel is typically used tocarry HSDPA related information/signalling as well as other dedicateddata such as speech and control data. The user equipment may communicatewith several base stations at the same time. For example, the associateddedicated channel may be in soft handover.

In addition to associated dedicated channels, the HS-DSCH may beassociated also with a shared control channel (SCCH). The SCCH can beused to carry HS-DSCH specific information/signalling to those usersreceiving data on the HS-DSCH.

A current proposal is to use the dedicated channel to inform the userequipment that it has data to be read on the HS-DSCH and SCCH. That is,only those users receiving data at a given time will receive anindication on the dedicated channel. The dedicated channel may be calledas a pointer channel since it points to the shared channels. Thededicated channel may also contain information about modulation andcoding schemes, power levels and similar parameters used for the sharedchannels. This information can be sent also on the shared channel. Theshared control channel on the other hand is used to carry informationthat is specific to the data transmitted on the shared data channel(HS-DSCH). This information can contain for instance packet numbers forthe HARQ and so on. The shared control channel can be sent on a separatecode channel (code multiplexed) or using the same code channels asHS-PDSCH (time multiplexed).

Unlike the dedicated channel, the HS-DSCH is assumed not to be in softhandover. That is, each base station is assumed to have their own sharedchannel and the user equipment is assumed to receive data from only onebase station at a time. The so called fast cell selection (FCS)technique may be used to switch the data transmission from one basestation to another. However, the shared channels does not use powercontrol. Instead, the shared channels are proposed to be transmittedwith fixed or semi-fixed power. The term ‘semi-fixed’means in here thatthe power is not changed often. The power could, for instance, be a cellspecific parameter.

In the currently proposed arrangements the high speed downlink sharedchannel (HS-DSCH) is planned to be associated with a dedicated channelwhich would carry in the downlink at least information regarding thetiming when the receiving station is to receive on a shared channel. Theassociated dedicated channel may possibly carry also other information.In the uplink, the associated dedicated channel may carry, for example,the required acknowledgements (ACK) for a fast HARQ.

The inventor has found that this way be problematic for example in thecontext of the uplink power control of the fast HARQ acknowledgements. Aproblematic situation may occur especially when the associated dedicatedchannel is in the soft handover mode. During the soft handover theuplink power is adjusted in accordance with the best quality uplinkamong an active set of base stations. However, signalling on the highspeed shared channel may be transmitted from another base station. Thecommunication link between the user equipment and said other basestation may be of poorer quality than said best uplink connection.Nevertheless, said other base station expects to receive responses suchas an acknowledgement from the user equipment. Since the quality of thisuplink connection may be of substantially poorer quality than what thebest uplink is, there is a risk that the response is not properlyreceived and decoded or is not received at all.

The fast cell selection function may be used to guarantee in someoccasions that best possible downlink is utilised for communicationtowards the user equipment. However, the base station that provides thebest uplink may be different than the base station providing the bestdownlink. This may be so, for example due to fast fading or otherchanges in the signalling conditions. This may increase theunreliability of the responding functionality.

The prior art proposals for solving this problem include so calledstrong coding, e.g., by using repetition coding. In the repetitioncoding the acknowledgement (ACK) bit or bits is/are repeated severaltimes. This, however, may cause too much additional load on the airinterface and/or reserve too much of the radio resources if one wants toguarantee the correct reception of the acknowledgement message.

Another prior art proposal is the so called fixed power offset foracknowledgement (ACK) transmissions. This means that all acknowledgementmessages are transmitted with increased or a certain power in order toensure that the acknowledgement is received even through the poorestquality uplink. However, even a fixed power level for acknowledgementmessages may not completely solve the problem of substantially poorsignalling conditions. Thus situations where the power is not highenough may still occur. On the other hand, it is also possible that thefixed power level is unnecessarily high. Thus, in addition toreliability problems this approach may be disadvantageous in that toohigh power is used by the user equipment causing interference andunnecessarily high power consumption.

SUMMARY OF THE INVENTION

Embodiments of the present invention aim to address one or several ofthe above problems.

According to one aspect of he present invention, there is provided amethod for communication between a first station and a second station,comprising: communicating from the first station to the second stationinformation associated with the manner how the second station shouldtransmit towards the first station; and transmitting from the secondstation based on said information from said first station instead oftransmitting in a manner the second station would have transmitted hadit not been provided with said information.

In a specific embodiment said information is transmitted on a dedicatedchannel from the first station to the second station.

In another specific embodiment said information is communicated in amessage that is transmitted from the first station to a second station.A response to the message is then transmitted from the second stationbased on said information.

The second station may transmit with a transmission power that has beenset based on said information after having received the information.

The second station may repeat the transmission, the number oftransmissions depending on said information.

Said information may define an offset parameter, the power level of thetransmission being shifted an amount as indicated by said offsetparameter or the transmission.

In an additional step the quality of the interface between the first andsecond stations is determined. The information to be transmitted to thesecond station is then defined by the first station based on saiddetermination.

The second station may be in communication with at least one furtherstation, said further station providing control instructions to thesecond station. The second station may be involved in a handover betweensaid at least two stations. The second station may be in a soft handovermode.

According to another aspect of the present invention there is provided acommunication system comprising: a station; a user equipment forcommunication with the station via a wireless interface, said userequipment being adapted to control at least one transmission parameter;and control means adapted for provision said user equipment withinformation associated with a transmission parameter for use by the userequipment when transmitting to the station, the user equipment beingenabled to transmit with a different transmission parameter based onsaid information than what the transmission parameter would be if theuser equipment had not been provided with said information.

At least one further station may be provided, said further station beingadapted for communication with the user equipment, the arrangementpreferably being such that the user equipment is adapted to followcontrol instructions from said further station unless said informationis provided thereto.

According to another aspect of the present invention there is provided astation for a communication system comprising control means forgenerating a message to be communicated from the station to anotherstation, said control means being adapted to provide said other stationwith information associated with a parameter for use by said otherstation for use in control of communication from said other station tothe station when responding the message.

According to another aspect of the present invention there is provided auser equipment for communication with a station of a communicationsystem via a wireless interface, comprising means for receiving amessage from the station and control means for transmitting a responseto the message, wherein the user equipment is adapted to transmit theresponse in accordance with control information received with themessage.

BRIEF DESCRIPTION OF DRAWINGS

For better understanding of the present invention, reference will now bemade by way of example to the accompanying drawings in which:

FIG. 1 shows an access system wherein the present invention may beembodied;

FIG. 2 is a flowchart illustrating the operation of an embodiment of thepresent invention; and

FIG. 3 shows a specific embodiment.

FIG. 4 illustrates exemplary offset commands sent from the basestations.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

An embodiment will now be described with reference to a mobiletelecommunication system. The exemplifying communication systemcomprises a radio access part adapted to operate based on the WCDMA(Wideband Code Division Multiple Access) technique. A feature of theWCDMA based systems is that a plurality of user equipment is allowed tocommunicate with a base transceiver station in a cell over a radiointerface (only one user equipment, however, is shown in FIG. 1 forclarity). As shown by FIG. 1, a user equipment is also allowed to be inradio communication with more than one base station at the same time.FIG. 1 shows only two base stations BS1, BS2 for clarity.

The user equipment comprises a mobile station MS1. The term mobilestation refers to a mobile user equipment that is enabled to move from alocation to another. A mobile station may also roam from one network toanother network, if the other network is compatible with the standardthe given mobile station is adapted to and there is a roaming agreementbetween the operators of the two networks.

Each of the base stations BS1, BS2 may be provided with a controllerentity BCE. The controller entity may be adapted to perform varioustask, such as to measure and control power levels that are used forcommunication between the base station and the mobile station MS1. Inaddition to the controller entity of the base station, the operation ofthe base station may also be controlled by at least one furthercontroller entity, such as a radio network controller NC. Thearrangement is typically such the various control functions associatedwith a base station are divided between the controller entity of thebase station and a network controller entity. A network controllerentity may be adapted to control one or several base stations. Thevarious network controller entities may be connected to each other forcommunication therebetween.

Communication between the mobile station and the base stations maycomprise any kind of data such as speech data, video data or other data.The base stations and mobile station communicate also control data. Thecontrol data may associate with management operations. The control datamay comprise messages such as various request and acknowledgements.

Data may be transmitted between the stations as a plurality of datasymbols in subsequent data or radio frames. The signals carrying thedata may be transmitted with variable data symbol transmission rates(data speeds), wherein the transmission rate may be different insubsequent frames of the transmission. The data symbols may betransmitted based on different access techniques. For example, in theCDMA (Code Division Multiple Access) system data is encoded fortransmission by processing data symbols to be transmitted by a spreadingcode for each transmission channel. In the TDMA (mime Division MultipleAccess) system data is transmitted in different time slots allocated fordifferent channels.

The communication between the mobile station MS1 and the base stationsBS1 and BS2 may occur via different communication channels, such as viaa dedicated channel, shared channel and so on. In some systems such asthe CDMA the channels may be distinguished from one another by the useof scrambling codes in a manner which is known by the skilled person.

In FIG. 1 the different signalling conditions between the mobile stationand the base stations are illustrated by different widths of the arrowsbetween the stations. As shown, base station BS1 has a weaker uplinkwith the mobile station MS1 than the other base station BS2. Thisimplies that the power control of the uplink follows the base stationBS2. However, as shown in FIG. 1, the downlink from base station BS1 maybe stronger than what the downlink from the base station BS2 is.

Each of the base stations of FIG. 1 may be enabled to measure one ormore parameter that associate with the connection. The parameter may bea quality parameter such as the power levels or signal to interference(SIR) level in the uplink. That is, the power level or SIR level atwhich each base station BS1, BS2 receives from the mobile station MS1may be known by the respective base station.

The power control mechanism in the access network is typically such thatthe mobile station MS1 follows the power commands received from the“strongest” base station, e.g. the base station BS2 that receives thesignal transmitted by MS1 with the best quality parameter. Thetransmission power of the mobile station MS1 is then adjustedaccordingly even if the other base station BS1 keeps on asking for moretransmission power. This is so since the mobile station MS1 onlyincreases transmission power if all those base stations that are in softhandover with the mobile station MS1 ask for more power.

In the following example it is assumed that in normal operation themobile station MS1 adjusts it transmission power based on the powercommands received from the base station BS2. The power adjustmentmechanism may be based on use of the so called quality target or powerthreshold values. If the quality of the connection is below the targetvalue, the mobile station MS1 is asked to increase the transmissionpower and if the quality is above the target, the power is asked to bedecreased.

The connection quality target can be announced e.g. by means of socalled Eb/No (Signal Energy/Noise) or SIR (Signal to Interference Ratio)or desired signal level target or a similar parameter indicating aquality measure which can be estimated for the connection between twostations.

The quality of the connection is controlled based on the target value.Any of the connection parameters that have influence to the quality ofthe connection should follow any changes in the target. In most cases itis sufficient if the transmission power is increased/decreased in orderto meet the quality target value. A more detailed description of apossible closed loop power control mechanism can be found, for example,from 3GPP (third generation partnership project) technical specificationNo. TS25.214 “Physical layer procedures (FDD)”.

In addition to the closed loop power control mechanism the CDMA systemsmay include also an outer loop power control mechanism. This may adjustthe power or SIR target based on other quality target parameters such asthe bit error rate (BER) or frame error rate (FER) or any other similarquality target the connection should meet.

In the embodiments a first station may transmit data or a request or anenquiry to a second station. After reception of said transmission thesecond station then transmits a response back to the first station. Toimprove the reliability and/or optimise the use of resources,information associated with at least one parameter for the response issignalled from the first station to the second station. This parametermay, for example, associate with the required power levels of theresponse and/or the number of times the response shall be transmittedand so on. The response signalling is then performed based on thereceived information.

In the FIG. 1 example the first station is the base station BS1 and thesecond station is the mobile station MS1. For example, when the basestation BS1 allocates a channel to the mobile station MS1 and sends datathereto on the high speed data shared channel (HS-DSCH), the basestation BS1 expects the mobile station to return an acknowledgement(ACK).

The base station BS1 may provide the mobile station with information onan associated control channel (either dedicated or shared) regarding thepower levels required for the response. In a preferred embodiment theinformation provides the mobile station MS1 with an offset value. Theoffset value indicates the difference in power relative to power levelused for transmission in the best uplink with the base station BS2. Thebase station MS1 determines the offset that is needed for the reliableacknowledgement transmission from the mobile station MS1 based on one ormore measurements associated with transmissions from the mobile station.The power is determined such that a predefined level of reliability isobtained for the decoding of the acknowledgement at the base stationBS1.

The mobile station MS1 is provided with appropriate power control entityPC. A per se known power control entity can be adapted to incorporate afeature that enables adjustment of the response transmission powerlevels based on the information received from the base station BS1. Thatis, the power control entity of the mobile station may make a decisionthat the response transmission needs to be accomplished in a differentpower level than what is used or communication with the best basestation BS2 and control the transmission accordingly.

The acknowledgement message (ACK) may be transmitted base to the basestation BS1 on a dedicated channel. The dedicated channel may be ‘on’all the time even if there is no acknowledgements to be sent. This is soin order to keep the closed loop power control running. The active basestation BS1 may measure a quality parameter such as the signal tointerference ratio (SIR) of this dedicated channel for overall powercontrol purposes. This may be done e.g. based or so called pilot bitsthat are transmitted by the mobile station. Thus the base station BS1can calculate a required power offset. The power offset requirement issignalled from the base station BS1 to the mobile station MS1 with thedownlink data packet to tell the mobile MS1 how much more power isrequired for the acknowledgement transmission.

New signalling bits may be added in the downlink transmission from thebase station BS1 to tell the required power offset for the userequipment MS1. These bits may be sent, e.g., on the shared controlchannel since only the user equipment or those user equipment receivingon the downlink shared data channel need to send the acknowledgementACK. That is, this information is not needed all the time, but only whenthere is data packets to acknowledge. Alternatively, the base stationmay sent these bits to the user equipment via a dedicated controlchannel or dedicated data channel.

The power control may be accomplished in a slot by slot basis in accesstechniques wherein the transmissions occur in slots.

A transmission can be divided into the slots e.g. based on time or bymeans of a spreading code. The mobile station MS1 may be adapted toassign power for the slots in accordance with a “normal” power controlmechanism unless the mobile station has been provided with informationwhich requires use of a different power level for a slot (or severalslots) that are allocated for the response.

In a simple case one bit may be enough for the provision of the abovereferenced information. For example, ‘0’ could indicate that an offsetof 5 dB is required and ‘1’ could indicate an offset of 10 dB. Accordingto another possibility ‘0’ could indicate that no offset is required and‘1’ could indicate that a predefined additional power is required.

2 to 4 bits may be used in a typical application for defining 4 to 16different power offset levels. A step between the different power levelsmay be, for example, 2, 5 or 10 dB. Alternatively the step size betweenthe power levels may be adapted to change nonlinearly.

FIG. 2 illustrates a flowchart of the operation of an embodiment of theinvention. The method begins at step 201, where a quality parameter forcommunication from a user equipment is measured. The method continues tostep 202, where based upon the measurement, the transmission power theuser equipment should use is determined. The method then continues tostep 203, where the message is transmitted to the user equipment, themessage including information associated with the determinedtransmission power. The method then continues to step 204, where themessage and the information associated with the determined transmissionpower is received by the user equipment. The method then continues tostep 205, where the user equipment responds to the message bytransmitting with a transmission power that has been adjusted based uponthe information associated with the determined transmission power.

A more specific embodiment will now be described with reference to FIG.3 showing transmission of data packets between a base station (node B)and two user equipment UE1 and UE2. It shall be appreciated thatalthough FIG. 3 shows channels in association with only one basestation, a plurality of base stations may have communication channelswith the user equipment UE1 and/or UE2 at the same time. Other channelsare, however, not shown for reasons of clarity.

A number of packets is shown to be transmitted to a first user equipmentUE1 and to a second user equipment UE2 on the data channel HSPDSCH. Thevertical lines of FIG. 3 dividing the transmission into sectionsindicate a high speed downlink packet access transmission time intervals(HSDPA TTI). The HSDPA TTI is a collection of a defined number of slots.That is, the high speed downlink packet access transmission timeinterval (TTI) defines a period for data transportation between userequipment and a base station via the high speed downlink shared channel(HSDSCH). Logically the TTI can thus be seen to correspond the conceptof data frames. In the FIG. 3 example eight TTIs are shown, each TTIbeing three slots in length.

In the following it is assumed that the acknowledgements are provided inaccordance with the fast hybrid automatic repeat request (HARQ) scheme.A so called N-channel HARQ is also assumed to be used for the fast HARQtogether with a so called stop-and-wait protocol. The stop-and-waitprotocol may be used in order to reduce buffering requirements of thereceiving station.

The N-channel HARQ supports asynchronous transmission. Thus differentusers can be scheduled freely without need to wait for completion of agiven transmission. The receiving station may need, however, to know towhich HARQ process the packet belongs to. This information can beexplicitly signalled on a high speed downlink packet access (HSDPA)control channel (CH), e.g. the SCCH. For example, after three packetshave been transported to the first user equipment UE1, two packets maybe transmitted to the second user equipment UE2. The transmission to thefirst user equipment UE1 may in such case be delayed by two TTIs. Theprocessing times of data packet to different user equipment should bedefined such that continuous transmission to a user equipment ispossible.

Each packet is preferably acknowledged during the transmission of otherpackets so that the downlink (DL) channel can be kept occupied all thetime when there are packets to be transmitted.

In FIG. 3 the uplink acknowledgements are shown to be transmitted on thededicated physical control channel (DPCCH). Arrows R1 to R9 indicatevarious relations between different operations. That is, relationsbetween pointer bits on the DL DPCH, shared data and control channel(HS-PDSCH and SCCH) transmission and the acknowledgement transmissions.

More particularly, each of the double lined arrows R2, R5 and R9indicates a quality measurement performed for the uplink of a given userequipment on the respective dedicated control channel. The single linedarrows R1, R4 and R6 indicate the relationships between the pointer bitsand shared control channel SCCH in the downlink. The single lined arrowsR3 and R6 indicate the relationships between the downlink data channelHSPDSCH and acknowledgements in the uplink. The acknowledgements aretransmitted with a power that has been adjusted based on informationreceived on the SCCH, that is based on he results of the measurements.

During the first interval TTI1 the base station transmits a pointer bitto the user equipment UE1. The pointer bit indicates that the userequipment UE1 shall receive data and control information during the nextTTI (TTI2) on the HS-PDSCH and on the SCCH. Also during TTI1, the basestation measures the quality of the uplink of the user equipment UE1.These relations are shown by the relation arrows R1 and R2,respectively.

For example, the SIR of the uplink can be measured from the dedicatedpilot symbols transmitted on the DPCCH in every slot. Based on thisquality measurement, the base station provides the user equipment UE1 inthe TTI2 with information regarding the power level that should be usedwhen transmitting the acknowledgement during TTI4. This relation isindicated by arrow R3. The power level information can be provided as apower offset, as explained above. This power offset information may be,for example, provided as a field of a few bits in the shared controlchannel (SCCH).

It should be noted that the measurements may be averaged over a longerperiod of time or otherwise processed. The arrow R2 simply shows thatthe power offset used for the transmission is based on themeasurement(s) done before the transmission of the power offset.

After having received the power level information the user equipment UE1sends the acknowledgement using a power level that is based oninformation from the base station. The acknowledgement may be a positiveacknowledgement (A in FIG. 3) or a negative acknowledgement (N in FIG.3).

In FIG. 3, some of the acknowledgement slots are shown to be higher inorder to illustrate that increased transmit power is used for theseacknowledgements. The increased power may be applied for the whole slotor only on the acknowledgement bits within the slot. The same increasedpower may also be used in other slots if they contain other informationsuch as measurement or quality report which is sent only to the samebase station as the acknowledgement. The increased power may also beapplied to the entire TTI or even a number of TTIs.

In addition to relations R1 to R3, FIG. 3 illustrates also a second setof relations R4 to R9 that associate with the user equipment UE2. Inthis case the acknowledgement was negative (N) and therefore a newpointer bit was given on the DL CPCH channel of the second userequipment UE2 for retransmission of the message.

In order to ensure that the power level for the response can bedetermined appropriately by the base station the uplink qualitymeasurement is preferably accomplished as late as possible. As shown,information associated e.g. with the measurement as indicated by thearrow R2 is transmitted in the next transmission time interval (TTI2) onthe control channel (DLSCCH).

The embodiments are especially suitable for acknowledgements because theacknowledgements need to be sent in response to a downlink transmissionand also because the reliability of the acknowledgement transmissionshould be high.

The message specific control information may be signalled only when thefirst station determines that a different parameter is needed in orderto ensure a reliable response by the user equipment.

FIG. 4 shows a further embodiment in which the user equipment firstfollows power commands from the strongest base station, that is from abase station BS2. Another base station BS1 sends a ‘power offset1’message to the user equipment. After having received the ‘power offset1’message the power control function of the user equipment starts tofollow said other base station.

The user equipment power control may set its transmission power based onthe message from the base station BS1 for a predetermined time. The userequipment may alternatively follow the commands from the base stationBS1 as long as it has some information, such as acknowledgements ormeasurement reports or so on to be sent to this base station. The userequipment may also wait for new power offset information from any of thebase stations it is in connection with. That is, a new offset such asthe shown ‘Offset2’ will replace the previous offset parameter.

When the user equipment power control returns to the “normal” softhandover mode the user equipment may change (typically decrease) itspower back to the level it used before receiving the offset command‘Ofset 1’. That is, the user equipment may start to follow the powercontrol commands from the strongest base station BS2 having the bestuplink with the user equipment. This may be accomplished by using anoffset parameter that equals the first offset (i.e. offset2=offsetl inFIG. 4) informed by the base station BS1 or a predetermined secondoffset (offset2). The second offset may be a function of the said firstoffset. The second offset may also be informed by the base station BS2having the best uplink

In a further embodiment each base station in connection (for instance,in a soft handover) with the user equipment may continuously measure thequality of the uplink. In addition to or instead of the normal powercontrol commands each of the base stations may send power offsetinformation to the user equipment telling how much the power should hechanged (increased or decreased) in order to meet the quality target.This information is preferably sent on the dedicated control channel. Ina normal soft handover case the user equipment may then use the offsetthat results in the lowest transmission power or alternatively followthe normal power control commands. However, when the user equipment hassomething to send to one base station only, the user equipment may thenuse the power offset sent by that base station. The offset may be sentperiodically, e.g., in each slot as the power control commands, or onceper every n slots and so on. The offset information may also be sentwhen needed, e.g., when the value of the offset exceeds some thresholdvalues.

In an embodiment the user equipment may also be forced to use strongercoding for the transmission of the acknowledgement message. For example,the user equipment may be instructed to transmit the acknowledgementrepeatedly. For example, instead of sending the acknowledgement once theuser equipment may be instructed to transmit the acknowledgement three,five, or ten times and so on. According to an embodiment the userequipment is instructed to transmit the acknowledgement e.g. in threeslots instead of one slot so that the acknowledgement can be decodedreliably.

The above discussed transmission parameter information provisionmechanism may also be used in connection with other signalling functionsthan acknowledgements. The response messages could be, for example,measurement reports or other reports. The herein proposed signallingmechanism may be especially advantageous if a report is requested by abase station of a plurality of base stations in communication with auser equipment. The base station may inform the user equipment of thepower offset and/or any other parameter that is to be used for theresponse towards the specific base station.

The above discussed adjustment of at least one feature of the responsesignalling based on information from power level measurements. Theadjustment may also be based on other information that associates withthe interface between the two stations. For example, the base stationBS1 may request for a certain power offset based on analysis of theprevious responses from the mobile station MS1. If the analysisindicates that a certain number of responses has not been correct, theoffset may be increased in order to improve the reliability. Theresponses may be earlier ACKs or other data transmitted from the userequipment, e.g., speech packets.

It is noted that the above disclosed solution is applicable also ininstances where the first message is sent from the user equipment to abase station. In such a case the user equipment may inform the basestation of any requirements that it may have for the response from thebase station.

It shall be appreciated that whilst embodiments of the present inventionhave been described in relation to mobile stations, embodiments of thepresent invention are applicable to any other suitable type of userequipment.

It shall be appreciated that whilst embodiments of the present inventionhave been described in relation to a mobile station that is incommunication with more than one base station, the present invention isapplicable also to instances where only two station are in communicationwith each other. For example, a first station transmitting a messagethat is to be responded by a second station may insert in the messageinformation regarding e.g. coding and/or power that is to be used forresponding to the particular packet.

It shall be appreciated that while this specification mentions somesystem specific examples of the communication channels the embodimentsof the invention are not restricted by these examples.

The response may also be sent, for example, on a shared control channelor a data channel in systems where such a channel is defined. A specificacknowledgement channel may also be defined.

The data is described as being in packet form. In alternativeembodiments of the invention the data may be sent in any suitableformat.

In addition, it is not always necessary to measure the quality of theconnection for each data packet and/or to provide the user equipmentwith the offset information each time a response is required. Instead,the measurement may be accomplished and/or information transmitted e.g.in predefined intervals or in response to a redefined event (e.g. thequality of the connection has changed or the user equipment has beenrelocated from a network controller to another network controller and soon). It may thus be enough if the offset information is provided oncefor the user equipment during a connection between the user equipmentand a base station.

The embodiment of the present invention has been described in thecontext of a CDMA system. This invention is also applicable to any otheraccess techniques including time division multiple access, frequencydivision multiple access or space division multiple access as well asany hybrids thereof.

It shall be appreciated that the base station may in some communicationstandards, such as those associated with the 3^(rd)generation (3G)universal mobile telecommunications system (UMTS), be referred to asnode B. However, this specification has used the term base station forclarity.

According to an alternative solution for the above discussed problem adedicated physical channel (DPCH) is used only in association with ahigh speed downlink shared channel (HS-DSCH). That is, no other data istransmitted on the DPDCH. The power control of the DPCH may then followbase station that transmits on the active HS-DSCH (both in the uplinkand the downlink) instead of the best base station. If no other data istransported on the uplink DPDCH, then the uplink power control functionof the mobile station could follow the active high speed data basestation. In such a situation information regarding the power offset maynot be needed for the uplink, since the power control function mayadjust the power.

It is also noted herein that while the above describes exemplifyingembodiments of the invention, there are several variations andmodifications which may be made to the disclosed solution withoutdeparting from the scope of the present invention as defined in theappended claims.

1. A method comprising: receiving at a device in communication with atleast a first station via a wireless interface power control commandsfrom said first station and each of any other stations with which thedevice is also in simultaneous communication; receiving from a controlunit further control information associated with a transmissionparameter for use by said device for one or more transmissions to saidfirst station; and controlling at least one transmissions from saiddevice to said first station based on a power control command from thestation that receives transmissions from said device with the bestquality parameter, and based on said further control informationreceived from the control unit, wherein the further control informationcomprises a control command selected from a plurality of controlcommands by the control unit.
 2. A method according to claim 1, whereinthe further control information includes power offset informationregarding how much more transmission power is to be used for at leastone transmission from said device to said first station.
 3. A methodaccording to claim 2, wherein the power offset information indicateswhether an offset is required or whether a predefined additional poweris required.
 4. A method according to claim 2, wherein the power offsetinformation indicates whether an offset of a first value is required, orwhether an offset of a second value is required.
 5. A method accordingto claim 1, wherein the further control information specifies use ofstronger coding for said at least one transmission from said device tosaid first station.
 6. A method according to claim 1, wherein thefurther control information includes an instruction to repeat the atleast one transmission to said first station an increased number oftimes.
 7. A method according to claim 1, wherein said at least onetransmission from said device to said first station include anacknowledgement of data received at said device from said first station.8. A method according to claim 7, wherein the at least one transmissionsfrom said device to said first station include an acknowledgement ofdata received from said first station on a high speed data sharedchannel (HS-DSCH).
 9. A method according to claim 1, wherein said atleast one transmission from said device to said first station include ameasurement report or a quality report.
 10. A method according to claim1, wherein the further control information is sent in response to apredefined event.
 11. A method according to claim 1, wherein the furthercontrol information is provided once for the device during a connectionbetween the device and a base station.
 12. A method according to claim1, wherein the at least one transmission to said first station includeresponses to messages from the first station, and wherein said furthercontrol information is provided each time a response is required.
 13. Amethod according to claim 12, wherein the further control information isinserted in each message to which a response is required.
 14. A methodaccording to claim 12, wherein the messages from the first station areprovided on a data channel, and wherein the further control informationis provided on an associated control channel.
 15. A method according toclaim 1, wherein the at least one transmission to said first stationinclude responses to messages from the first station on a data channel,and wherein said further control information is provided on a controlchannel associated with said data channel.
 16. An apparatus. comprising:a receiver configured to receive power control commands from a firststation with which the apparatus is in communication via a wirelessinterface and also from any other stations with which the apparatus isalso in simultaneous communication; the receiver configured to receivefrom a control unit further control information associated with atransmission parameter for use by the apparatus for at least onetransmission to said first station; and a controller configured tocontrol at least one transmission from said apparatus to said firststation based on a power control command from the station that receivestransmissions from said apparatus with the best quality parameter, andbased on said further control information received from the controlunit, wherein the further control information comprises a controlcommand selected from a plurality of control commands by the controlunit.
 17. An apparatus according to claim 16, wherein the furthercontrol information includes power offset information regarding how muchmore transmission power is to be used for at least one transmission fromsaid apparatus to said first station.
 18. An apparatus according toclaim 17, wherein the power offset information indicates whether anoffset is required or whether a predefined additional power is required.19. An apparatus according to claim 17, wherein the power offsetinformation indicates whether an offset of a first value is required orwhether an offset of a second value is required.
 20. An apparatusaccording to claim 16, wherein the further control information specifiesuse of stronger coding for said at least one transmission from saidapparatus to said first station.
 21. An apparatus according to claim 16,wherein the further control information includes an instruction torepeat the at least one transmission to said first station an increasednumber of times.
 22. An apparatus according to claim 16, wherein said atleast one transmission from said apparatus to said first station includean acknowledgement of data received at said apparatus from said firststation.
 23. An apparatus according to claim 22, wherein the at leastone transmission from said apparatus to said first station include anacknowledgement of data received from said first station on a high speeddata shared channel (HS-DSCH).
 24. An apparatus according to claim 16,wherein said at least one transmission from said apparatus to said firststation include a measurement report or a quality report.
 25. Anapparatus according to claim 16, wherein the further control informationis sent in response to a predefined event.
 26. An apparatus according toclaim 16, wherein the further control information is provided once forthe apparatus during a connection between the apparatus and a basestation.
 27. An apparatus according to claim 16, wherein the at leastone transmission to said first station include responses to messagesfrom the first station, and wherein said further control information isprovided each time a response is required.
 28. An apparatus according toclaim 27, wherein the further control information is inserted in eachmessage to which a response is required.
 29. An apparatus according toclaim 27, wherein the messages from the first station are provided on adata channel, and wherein the further control information is provided onan associated control channel.
 30. An apparatus according to claim 16,wherein the at least one transmission to said first station includeresponses to messages from the first station on a data channel, andwherein said further control information is provided on a controlchannel associated with said data channel.
 31. An apparatus for use in asystem in which a device is in communication with at least a firststation via a wireless interface and receives power control commandsfrom said first station and each of any other stations with which thedevice is also in simultaneous communication, the apparatus comprising:control unit configured to provide the device with further controlinformation associated with a transmission parameter for use by saiddevice for one or more transmissions to said first station wherein thefurther control information comprises a control command selected from aplurality of control commands by the control unit, and is used by thedevice together with a power control command from the station thatreceives transmissions from said device with the best quality parameterto control at least one transmission from said device to said firststation.
 32. An apparatus according to claim 31, wherein the furthercontrol information includes power offset information regarding how muchmore transmission power is to be used for at least one transmission fromsaid device to said first station.
 33. An apparatus according to claim32, wherein the power offset information indicates whether an offset isrequired or whether a predefined additional power is required.
 34. Anapparatus according to claim 32, wherein the power offset informationindicates whether an offset of a first value is required or whether anoffset of a second value is required.
 35. An apparatus according toclaim 31, wherein the further control information specifies the use ofstronger coding for said at least one transmissions from said device tosaid first station.
 36. An apparatus according to claim 31, wherein thefurther control information includes an instruction to repeat the atleast one transmissions to said first station an increased number oftimes.
 37. An apparatus according to claim 31, wherein said at least onetransmissions from said device to said first station include anacknowledgement of data received at said device from said first station.38. An apparatus according to claim 37, wherein the at least onetransmissions from said device to said first station include anacknowledgement of data received from said first station on a high speeddata shared channel (HS-DSCH).
 39. An apparatus according to claim 31,wherein said at least one transmissions from said device to said firststation include a measurement report or a quality report.
 40. Anapparatus according to claim 31, wherein the further control informationis sent in response to a predefined event.
 41. An apparatus according toclaim 31, wherein the further control information is provided once forthe device during a connection between the device and a base station.42. An apparatus according to claim 31, wherein the at least onetransmission to said first station include responses to messages fromthe first station, and wherein said further control information isprovided each time a response is required.
 43. An apparatus according toclaim 42, wherein the further control information is inserted in eachmessage to which a response is required.
 44. An apparatus according toclaim 42, wherein the messages from the first station are provided on adata channel, and wherein the further control information is provided onan associated control channel.
 45. An apparatus according to claim 31,wherein the at least one transmission to said first station includeresponses to messages from the first station on a data channel, andwherein said further control information is provided on a controlchannel associated with said data channel.
 46. A method for use in asystem in which a device is in communication with at least a firststation via a wireless interface and receives power control commandsfrom said first station and each of any other stations with which thedevice is also in simultaneous communication, the method comprising:providing the device with further control information associated with atransmission parameter for use by said device for at least onetransmission to said first station, wherein the further controlinformation comprises a control command selected from a plurality ofcontrol commands by a control unit, and is used by the device togetherwith a power control command from the station that receivestransmissions from said device with the best quality parameter tocontrol at least one transmission from said device to said firststation.
 47. A method according to claim 46, wherein the further controlinformation includes power offset information regarding how much moretransmission power is to be used for at least one transmission from saiddevice to said first station.
 48. A method according to claim 47,wherein the power offset information indicates whether an offset isrequired or whether a predefined additional power is required.
 49. Amethod according to claim 47, wherein the power offset informationindicates whether an offset of a first value is required or whether anoffset of a second value is required.
 50. A method according to claim46, wherein the further control information specifies the use ofstronger coding for said at least one transmission from said device tosaid first station.
 51. A method according to claim 46, wherein thefurther control information includes an instruction to repeat the atleast one transmission to said first station an increased number oftimes.
 52. A method according to claim 46, wherein said at least onetransmission from said device to said first station include anacknowledgement of data received at said device from said first station.53. A method according to claim 52, wherein the at least onetransmission from said device to said first station include anacknowledgement of data received from said first station on a high speeddata shared channel (HS-DSCH).
 54. A method according to claim 46,wherein said at least one transmission from said device to said firststation include a measurement report or a quality report.
 55. A methodaccording to claim 46, wherein the further control information is sentin response to a predefined event.
 56. A method according to claim 46,wherein the further control information is provided once for the deviceduring a connection between the device and a base station.
 57. A methodaccording to claim 46, wherein the at least one transmissions to saidfirst station include responses to messages from the first station, andwherein said further control information is provided each time aresponse is required.
 58. A method according to claim 57, wherein thefurther control information is inserted in each message to which aresponse is required.
 59. A method according to claim 57, wherein themessages from the first station are provided on a data channel, andwherein the further control information is provided on an associatedcontrol channel.
 60. A method according to claim 46, wherein the atleast one transmissions to said first station include responses tomessages from the first station on a data channel, and wherein saidfurther control information is provided on a control channel associatedwith said data channel.